PHP 5.6.0 released

list

(PHP 4, PHP 5)

listانتصاب متغیرها به عنوان آرایه

Description

array list ( mixed $varname [, mixed $... ] )

مانند array() تابع واقعی نیست اما ساختار زبانی است. list() برای انتصاب فهرستی از عملوندها استفاده می‌شود.

Parameters

varname

متغیر.

Return Values

بازگرداندن آرایه انتصاب داده شده.

Examples

Example #1 مثال‌های list()

<?php

$info 
= array('coffee''brown''caffeine');

// Listing all the variables
list($drink$color$power) = $info;
echo 
"$drink is $color and $power makes it special.\n";

// Listing some of them
list($drink, , $power) = $info;
echo 
"$drink has $power.\n";

// Or let's skip to only the third one
list( , , $power) = $info;
echo 
"I need $power!\n";

// list() doesn't work with strings
list($bar) = "abcde";
var_dump($bar); // NULL
?>

Example #2 مثال استفاده list()

<table>
 <tr>
  <th>Employee name</th>
  <th>Salary</th>
 </tr>

<?php

$result 
mysql_query("SELECT id, name, salary FROM employees"$conn);
while (list(
$id$name$salary) = mysql_fetch_row($result)) {
    echo 
" <tr>\n" .
          
"  <td><a href=\"info.php?id=$id\">$name</a></td>\n" .
          
"  <td>$salary</td>\n" .
          
" </tr>\n";
}

?>

</table>

Example #3 استفاده از list() داخل یکدیگر

<?php

list($a, list($b$c)) = array(1, array(23));

var_dump($a$b$c);

?>
int(1)
int(2)
int(3)

Example #4 استفاده از list() به همراه اندیس آرایه‌ّای

<?php

$info 
= array('coffee''brown''caffeine');

list(
$a[0], $a[1], $a[2]) = $info;

var_dump($a);

?>

تولید خروجی زیر (ترتیب همان ترتیب در دستور list() است):

array(3) {
  [2]=>
  string(8) "caffeine"
  [1]=>
  string(5) "brown"
  [0]=>
  string(6) "coffee"
}

Notes

Warning

list() مقادیر را با شروع از سمت راست ترین پارامتر انجام می‌دهد. اگر از متغیرهای ساده استفاده می‌کنید نیاز به نگرانی در این باره ندارید. اما اگر از آرایه‌ها اندیس‌دار استفاده می‌کند همان ترتیب اندیس‌ها را انتظار داشته باشید که list() از چپ به راست نوشتید; که این طور نیست و برعکس آن است.

Note:

list() تنها بر آرایه‌های عددی کار می‌کند و فرض بر این است که اندیس از 0 شروع می‌شود.

See Also

  • each() - Return the current key and value pair from an array and advance the array cursor
  • array() - Create an array
  • extract() - Import variables into the current symbol table from an array

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User Contributed Notes 11 notes

up
33
chris at chlab dot ch
1 year ago
The example states the following:
<?php
// list() doesn't work with strings
list($bar) = "abcde";
var_dump($bar);
// output: NULL
?>

If the string is in a variable however, it seems using list() will treat the string as an array:
<?php
$string
= "abcde";
list(
$foo) = $string;
var_dump($foo);
// output: string(1) "a"
?>
up
21
svennd
1 year ago
The list() definition won't throw an error if your array is longer then defined list.
<?php

list($a, $b, $c) = array("a", "b", "c", "d");

var_dump($a); // a
var_dump($b); // b
var_dump($c); // c
?>
up
14
megan at voices dot com
11 months ago
As noted, list() will give an error if the input array is too short. This can be avoided by array_merge()'ing in some default values. For example:

<?php
$parameter
= 'name';
list(
$a, $b ) = array_merge( explode( '=', $parameter ), array( true ) );
?>

However, you will have to array_merge with an array long enough to ensure there are enough elements (if $parameter is empty, the code above would still error).

An alternate approach would be to use array_pad on the array to ensure its length (if all the defaults you need to add are the same).

<?php
    $parameter
= 'bob-12345';
    list(
$name, $id, $fav_color, $age ) = array_pad( explode( '-', $parameter ), 4, '' );
   
var_dump($name, $id, $fav_color, $age);
/* outputs
string(3) "bob"
string(5) "12345"
string(0) ""
string(0) ""
*/
?>
up
1
john at jbwalker dot com
8 months ago
The list construct seems to look for a sequential list of indexes rather taking elements in sequence. What that obscure statement means is that if you unset an element, list will not simply jump to the next element and assign that to the variable but will treat the missing element as a null or empty variable:

    $test = array("a","b","c","d");
    unset($test[1]);
    list($a,$b,$c)=$test;
    print "\$a='$a' \$b='$b' \$c='$c'<BR>";

results in:
$a='a' $b='' $c='c'

not:
$a='a' $b='c' $c='d'
up
0
vickyssj7 at gmail dot com
1 day ago
if we assign array's each value individual key('numeric only'), and use the array indices in list(),, then it output the reverse order of array keys--
BUT THE HIGHER KEY VALUE ("2" in this e.g below) WILL GET THE FIRST PLACE IN THE ARRAY IN RETURN, MEANS IT PUSHES THE VALUE WITH HIGHER KEY IN PLACE OF FIRST KEY VALUE, so it also gives higher key value the first priority while reversing the order of the keys and replacing the lower key value with the higher key value.

        $value = array( 0 => 'low', 2 => 'medium', 1 => 'higher');
        list($a[2], $a[1], $a[0]) = $value;
    var_dump($a);

//Outputs:---
array(3) {
            [0] => string(6) "medium"
            [1]  => string(6) "higher"
            [2]  => string(3) "low"
}
up
-4
edam
6 months ago
This doesn't work on associative array.  For example:

    list( $a, $b, $c ) = array( 'a' => 'a', 'b' => 'b', 'c' => 'c' );
    PHP Notice:  Undefined offset: 2 in Command line code on line 1
    PHP Notice:  Undefined offset: 1 in Command line code on line 1
    PHP Notice:  Undefined offset: 0 in Command line code on line 1
up
-3
Arne
1 year ago
list() will give an error if the input array is too short. This can be avoided by array_merge()'ing in some default values. For example:

<?php
$parameter
= 'name';
list(
$a, $b ) = array_merge( explode( '=', $parameter ), array( true ) );
?>
up
-3
Achilles at thegreatwarrior dot com
1 year ago
Second, when you’re using the list() function, you must acknowledge each array element. You could not do this
list($weekday, $month) = $date;

But you can use empty values to ignore elements:
list ($weekday, , $month) = $date;
up
-5
srikanth at networthindia dot com
1 year ago
Note: list cannot assign array cast of object to variables straight away. first you need to convert the object to numeric indexed array.

ex:
list($a, $b, $d) = (array) $abc; // $abc is an object; this will not assign.
list($a, $b, $c) = array_values((array) $abc); // This will work.
up
-7
Matt
1 year ago
You can't type check within the list() parameters:

list ( array $var1, $var2 ) = array ( array('one','two'), 'three');

generates a parse error, unexpected 'array'.
up
-5
Thanos K.
5 months ago
Also it seems that it doesn't work as expected with arrays with non numeric keys:

list($k, $l, $m) = array('a' => 'val1', 'b' => 'val2', 'c' => 'val3');

Gives empty variables..
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